Goodwill and Intangible Assets - Change in Carrying Value of Goodwill (Details) $ in Thousands	9 Months Ended
Sep. 30, 2020 USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2019	$ 63,924
Additions from exocad acquisition	340,181
Adjustments	23,237
Balance as of September 30, 2020	427,342
Clear Aligner
Goodwill [Roll Forward]
Balance as of December 31, 2019	63,924
Additions from exocad acquisition	43,500
Adjustments	2,695
Balance as of September 30, 2020	110,119
Systems and Services
Goodwill [Roll Forward]
Balance as of December 31, 2019	0
Additions from exocad acquisition	296,681
Adjustments	20,542
Balance as of September 30, 2020	$ 317,223

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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